1. 有害的;（尤指）有损健康的
Something that is harmful has a bad effect on something else, especially on a person's health.
harmful的反义词
e.g. ...the harmful effects of smoking...
吸烟的危害
e.g. It's believed the affair was potentially harmful to British aviation.
据信该事件可能对英国航空业造成不利影响。